The present invention relates to a method of feeding portions of wrapping material to a packing line.
In particular, the present invention relates to a method of dividing a continuous strip of wrapping material into single portions or sheets, and successively feeding the portions to a packing line consisting, for example, of an overwrapping line for packets of cigarettes or boxes or cartons containing a number of packets of cigarettes.
According to British Patent n. 1,550,136, a continuous strip is fed to a packing line using two separate supply lines arranged in series. The first feed unit upstream comprises two intermittent counter-rotating rollers substantially tangent to each other, and respective peripheral portions of which run along the strip; while the second feed unit comprises two continuous intermittently operated suction belts for retaining and drawing along respective lateral edges of the strip.
According to the above British patent, the portions of wrapping material are detached from the continuous strip using two separate cutting devices arranged in series along said path portion. More specifically, for detaching each sheet from the strip, the first cutting device makes two longitudinally aligned transverse lateral cuts in respective lateral edges of the strip between the two feed units; while the second cutting device, operating on the laterally cut strip portion under control of the second feed unit, makes a central cut in the strip to join the two lateral cuts and so detach the sheet. While still under control of the second feed unit, each sheet is then intercepted at a transfer station by the product for wrapping, by which it is pushed towards the packing line.
Cutting the sheets off the continuous strip in two stages is extremely advantageous in that it permits both the strip and the sheets to be fed exclusively by traction to the transfer station, thus eliminating any possibility of jamming, were the strip or sheets at any time to be pushed downstream as they travel towards the transfer station.
Though fairly satisfactory, the above device is particularly complex and expensive, due to featuring two cutting devices.